1. Field
Example embodiments generally relate to a low maintenance iron roughneck system with replaceable modular components thereof.
2. Related Art
Conventionally at an oil rig site, an iron roughneck is employed on rig floor where space is limited for drilling, drill pipe make-up and break out operations around the well center. FIGS. 1 through 4 illustrate a well known prior art iron roughneck, the ST-80C Iron roughneck manufactured by National Oilwell Varco®. Typically, the ST-80C requires a number of human operators to handle pipe make-up and break-out operations around the well center. The iron roughneck is typically installed on the drill floor utilizing either a single floor mounted socket or a floor mounted bearing an upper mast 30 attachment as shown in FIGS. 1 and 3 for elevated storage. With the taller column mast 30, the ST-80C is able to be stored above the crew, clearing drill floor space as is known.
One operator is at the hydraulic control station 50, while two (2) or more operators manipulate the scissor arm 35 which is attached between the mast 30 and a spinner 10A and torque wrench 20 (torque module) that is used for the drill pipe make-up and break out operations around the well center. This equipment is quite heavy (total assembly weight is about 7800 lbs) and can be extremely dangerous on the drill floor. For example, manual rotation of the conventional iron roughneck by human operators is required. The roughneck has to be muscled or pushed to rotate the unit in to place around the well center. The roughneck also has multiple levers that do different functions. Conventional roughneck systems such as is shown in FIGS. 1-4 allow the operator(s) to pull any lever or do any function at any time, even if it is dangerous to the operator or the roughneck; there are no safety interlocks in place. Further, installing the roughneck onto the drill pipe invites multiple hazards to personnel. With conventionally designed roughnecks, one or more operators are standing next to the roughneck while visually attempting to center the clamping device on the drill pipe.
Moreover, the roughneck needs frequent daily and scheduled maintenance, and it is prone to breakage. If one part of the roughneck is damaged, the entire system is out of order, costing significant downtime. There are also a number of zerks that are used to apply grease to the moving parts of the roughneck. The grease is used to try and keep contaminates out of the moving parts, which could cause damage. On the current roughnecks if this periodic maintenance is not performed, component damage will ensue. Daily downtime must also be scheduled for grease zerk maintenance.
Additionally, various diameters of piping are used in order to extract fossil fuels from deep beneath the earth's crust. The roughneck must be able to torque and spin various sections of different diameter pipes during the drilling process. The current roughnecks require that clamp dies be constantly changed to switch from one diameter of pipe to another. The changing or reconfiguring of the clamp dies takes time, slowing down the drilling process. The time it takes, “connection time”, delays extraction of oil and is a significant cost to drillers.
Accordingly, a site will typically have a number of different sized drill slips or drill collars and pipe handling devices to account for the different diameter piping used; i.e., a different sized drill slip or casing slip is used with each change in pipe diameter. Often this can mean up to 5 to 7 different diameter pipe handling devices such as slips, drill collars, tongs, as well as wasted time changing between these devices or changing the devices to different pipe sizes.
There are two, basic, conventional clamping methods used to hold pipe during torque operations on the pipe. The drill pipe is torqued at every tool joint or pipe joint, and a joint is present on drill pipe at about every thirty feet; thus requiring a torque operation at every joint. Drilling operations typically range from about 10,000 to 20,000 in depth, so hundreds of these torque operations are performed during the drilling process. The pipe must be clamped each time a torque operation is performed thereon.
One clamping method employs two clamp dies (clamps) placed directly across from each other. There is a problem if the pipe is not centered between the dies, the pipe can be damaged or slip out of the clamps, where one clamp die is located on each side of the pipe in a holder. This design applies all of the force in a small area about 1″ by 5″ on either side of the pipe; if the applied force is too high in this small area it will cause the pipe to become deformed, or “egg-shaped”, damaging the pipe. This setup also will occasionally cause the pipe to hit the edge of the dies, causing pipe damage on all pipes that are small or larger than the fixed radius between the clamps. Either of these conditions results in lost time due to the discarding of the pipe, or increased rate of pipe joint degradation which increases operating costs.
The second conventional clamping method employs three (3) fixed clamp dies (clamps) located in a holder set at a static mid-range radius in an effort to try and clamp different diameter pipes and distribute the force over a greater area. On pipe having a smaller diameter (and hence smaller radius), and due to the preset radius of the clamp dies in the holder, the smaller pipe only makes contact on the inside edge of the clamp dies only. Conversely, if the pipe diameter (and hence radius) is larger, the outside dies in the clamp holder will contact on the outside edge only. This becomes an issue, as pressure is not distributed evenly on the clamps during the torque operations.
In both design cases, if the pipe diameter changes, inserts must be either added or removed from the fixed jaw clamps in an effort to compensate for the radius change effect. Further, as the clamp dies provide only two points of pressure on the pipe, and not a uniform pressure, there is the possibility of slippage and/or deformation of the pipe under intense forces (typically in upwards of 100,000 ft-lbs) applied by the clamps to hold the pipe in place.
Conventionally, the torque applied to these clamps is applied by way of a cylinder with piston rod that is part of a torque module. The torque cylinder design is limited to 32 to 37 degrees of torque head rotation maximum in the conventional torque module. This is due to what is known as a cam over effect caused by the cylinder being fixed at one point to the back of the main body of the torque module support frame, so as the torque head rotates about the center of the pipe, the cylinder pushes the upper torque head around a radius or torque arc about the center of the drill pipe with the clamps engaged on the pipe, rotating the pipe. The rotational arc of the torque head will rotate to about 37 degrees maximum. At that point, the cylinder piston rod end reaches a point on the torque arc that is straight across or below a base attachment point where the cylinder attaches to the torque module frame. At this point, the cylinder can no longer be returned to its starting position around the torque arc. Instead, the cylinder will attempt to come straight across the torque arc and not follow the arc back around when it is returned. This will lock up or damage the torque head, so conventional torque modules are design limited to rotating the torque head up to a maximum of about 35 degrees, so as to prevent the cam over effect from happening.
Also this design has a major issue with the force angle changing from 90 degrees to less than 90 degrees as the cylinder in the torque module rotates around the torque arc. Torque is measured with the force applied at 1 ft and 90 degrees to the center of rotation. If the force angle increases or decreases from 90 degrees, the torque is decreased by the sine of the angle. So the torque accuracy of this conventional torque module design is limited, it will never yield a true torque and it cannot be compensated for due to the fact the operator does not know the required amount of rotation to achieve the desired torque.
This conventional hydraulic cylinder design in a torque module is also limited on break and make operations. The make operation (torqueing a pipe joint) is accomplished using the retraction side of the cylinder; the break operating is accomplished using the extension side of the cylinder. Because the break operation is performed using the extension side of the cylinder, the break operation becomes a two-step process. This is due to the fact that a cylinder puts out less force in a retract operation then it does in an extension operation due to the loss of area on the rod side of the cylinder. This limitation will cause what is referred to as the “breakout operation” (i.e., disconnect or breaking of the pipe joints one from the other) to be a two-step torque process instead of a single step. To breakout, the torque head of the conventional torque module with cylinder initially has to rotate to 35 degrees, then the clamp is applied to the pipe, and finally the clamped pipe under torque is rotated back breaking the tool joint apart. This two step torque process in the conventional torque module takes twice as long, as compared to a torque module that rotates from a central or neutral point and will rotate CCW or CW, for a single-step process. Moreover, the 37 degree limitation can also cause the torque process to require multiple movement steps, as a torque head rotation may require greater than a 37 degree movement on the pipe with the clamp.